linux-kernel - Re: Support sample context in perf report

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Date:   Thu, 7 Mar 2019 08:57:45 -0800
From:   Andi Kleen <andi@...stfloor.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Andi Kleen <andi@...stfloor.org>, acme@...nel.org,
        jolsa@...nel.org, namhyung@...nel.org,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: Re: Support sample context in perf report

On Thu, Mar 07, 2019 at 11:57:43AM +0100, Jiri Olsa wrote:
> On Tue, Mar 05, 2019 at 06:47:43AM -0800, Andi Kleen wrote:
> > [Changes: 
> > v4:
> > Address review comments. 
> > Fix --cpu filtering.
> > Fix a sampling bug.
> > Add support for configuring custom script menu entries in perfconfig.
> > Fix display of more samples than fit on screen.
> > Fix some buffer overruns in legacy code.
> > Add more tips
> 
> hi,
> getting gcc error on your branch, similar like last time:

Okay I figured out now why I'm not seeing this. It's because my perf
builds are with DEBUG=1, and Makefile.config has this insanity:

ifeq ($(DEBUG),0)
  ifeq ($(feature-fortify-source), 1)
      CFLAGS += -D_FORTIFY_SOURCE=2
  endif
endif

Anyways the warnings are false positives because the strings can never
be that big. In fact I think they're harmful because it discourages
adding safety margins to stack buffers.

Anyways you can use this patch as a workaround.

diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
index 364f5c577d00..3e795bd1279d 100644
--- a/tools/perf/ui/browsers/hists.c
+++ b/tools/perf/ui/browsers/hists.c
@@ -2554,7 +2554,7 @@ do_run_script(struct hist_browser *browser __maybe_unused,
 	}
 
 	if (act->time) {
-		char start[64], end[64];
+		char start[32], end[32];
 		unsigned long starttime = act->time;
 		unsigned long endtime = act->time + symbol_conf.time_quantum;